The present invention relates to an ink-jet head and the preparation method thereof, and further to a coating layer and the preparation method thereof. In particular, the present invention relates to an ink-jet head covered with a coating layer comprising poly-p-xylylene or a derivative of poly-p-xylylene to protect an electrode provided on an ink channel of the ink-jet head or an adhesive employed to make the ink-jet head, and the preparation method of the coating layer. The present invention also relates to a coating layer comprising poly-p-xylylene or a derivative of poly-p-xylylene, and the formation thereof. Hereafter, a coating layer comprising poly-p-xylylene or a derivative of poly-p-xylylene called as a parylene layer.
In some of electronic parts (or components) such as various semiconductor elements and devices such as ink-jet heads, which employ various materials such as metals, ceramics, and plastics, as a substrate body or substrate materials having said various materials on the surface, a protective layer, which comprises organic materials, is frequently provided on said substrate body for the purpose of enhancing electrical insulation, moisture resistance, and abrasion resistance Further, in order to minimize elution of components of adhesives from joined parts which are adhered employing said adhesives, a protective layer, which comprises organic materials, is occasionally formed in the same manner. Of such protective layers, a parylene layer, which is formed employing a gas phase synthetic method, is preferably employed, since it exhibits high insulating properties as well as high moisture resistance. However, due to the fact that said parylene layer exhibits low adhesion to a substrate body, Japanese Patent Publication No. 58-56371 describes enhancement of adhesion to a substrate body by forming a parylene layer after said substrate body is subjected to a pre-treatment employing a coupling agent.
The method described in Japanese Examined Patent Publication No. Tokkosho 58-56371 assures improved adhesion of said parylene layer to a substrate body, compared to conventional methods. However, the resultant adhesion is found to be insufficient. As a result, problems have occasionally occurred in which said layer is peeled off during the production process. In addition, problems with durability of products have occurred in which products result in layer peeling under product-using circumstances. Specifically, said problems are pronounced when a substrate body comprises an electrode comprised of metal. Further, said problems become serious in ink-jet heads in which a PZT substrate is employed as a piezoelectric substrate, and said electrode is provided on said PZT substrate. As a result, the resultant product yield has been adversely affected by said peeling. In such ink-jet heads, it is assumed that the formation of the parylene layer in the interior of the minute ink channels is one of factors of the low production yield.
From the viewpoint of the foregoing, the present invention was achieved. An object of the present invention is to provide a parylene layer which exhibits excellent adhesion to a substrate body as well as excellent durability, a parylene layer forming method capable of preparing such a parylene layer, and an ink-jet head prepared employing said parylene layer or a parylene layer which is formed employing said parylene layer forming method.
Another object of the present invention is to provide a parylene layer which exhibits excellent insulating properties as well as excellent heat resistance, a parylene forming method capable of preparing such a parylene layer, and an ink-jet head prepared employing said parylene layer or a parylene layer which is formed employing said parylene layer forming method.
Still another object of the present invention is to provide a parylene layer which results in an increase in yield without forming pinholes even though said layer is relatively thin, a parylene forming method capable of preparing such a parylene layer, and an ink-jet head prepared employing said parylene layer or a parylene layer which is formed employing said parylene layer forming method.
A further object of the present invention is to provide a parylene layer which can be prepared easily and at low cost, a parylene forming method capable of preparing such a parylene layer, and an ink-jet head prepared employing said parylene layer or a parylene layer which is formed employing said parylene layer forming method.
In order to achieve at least one of the aforesaid objects, the present invention was constituted as described below.
(1) An ink-jet head comprising:
(a) a substrate forming an ink channel having an electrode provided on an inner surface of the ink channel; and
(b) a coating layer covering the electrode, wherein the coating layer comprises poly-p-xylylene or a derivative of poly-p-xylylene admixed with a silane coupling agent.
(2) A process for forming an ink-jet head, comprising the steps of:
(a) providing an electrode on a surface of a substrate which forms an ink channel;
(b) placing the substrate provided with the electrode in a deposition chamber; and
(c) contacting the substrate with a vaporous poly-p-xylylene precursor or a vaporous poly-p-xylylene derivative precursor admixed with a vaporous silane coupling agent to form a coating layer onto the surface of the substrate.
(3) A process for forming an ink-jet head, comprising the steps of:
(a) providing an electrode on a surface of a substrate which forms an ink channel;
(b) placing the substrate provided with the electrode in a deposition chamber; and
(c) contacting the substrate with a vaporous poly-p-xylylene precursor or a vaporous poly-p-xylylene derivative precursor admixed with a vaporous silane coupling agent to form a coating layer onto the surface of the substrate, wherein at least a part of the silane coupling agent remains unvaporized in the deposition chamber during the step (c).
(4) An ink-jet head having an ink channel comprising a piezoelectric substrate provided with an electrode on an inner surface of the ink channel, wherein an ink droplet is jetted from the ink channel by deforming the piezoelectric substrate in accordance with an applied electric field, the ink-jet head comprising covering the electrode, wherein the coating layer comprises poly-p-xylylene or a derivative of poly-p-xylylene admixed with a silane coupling agent.
(5) A process for forming an ink-jet head jetting an ink droplet from the ink channel by deforming a piezoelectric substrate in accordance with an applied electric field, comprising the steps of:
(a) providing an electrode on a surface of the piezoelectric substrate which forms an ink channel;
(b) placing the piezoelectric substrate provided with the electrode in a deposition chamber; and
(c) contacting the piezoelectric substrate with a vaporous poly-p-xylylene precursor or a vaporous poly-p-xylylene derivative precursor in the presence of a vaporous silane coupling agent to form a coating layer onto the surface of the piezoelectric substrate.
(6) A process for forming an ink-jet head jetting an ink droplet from the ink channel by deforming a piezoelectric substrate in accordance with an applied electric field, comprising the steps of:
(a) providing an electrode on a surface of the piezoelectric substrate which forms an ink channel;
(b) placing the piezoelectric substrate provided with the electrode in a deposition chamber; and
(c) contacting the piezoelectric substrate with a vaporous poly-p-xylylene precursor or a vaporous poly-p-xylylene derivative precursor admixed with a vaporous silane coupling agent to form a coating layer onto the surface of the substrate, wherein at least a part of the silane coupling agent remains unvaporized in the deposition chamber during the step (c).
(7) An article comprising:
(a) a substrate; and
(b) a coating layer on the substrate, wherein the coating layer comprises poly-p-xylylene or a derivative of poly-p-xylylene admixed with a silane coupling agent.
(8) A process for forming a coating layer comprising poly-p-xylylene or a derivative of poly-p-xylylene on a substrate, comprising the steps of:
(a) placing the substrate in a deposition chamber; and
(b) contacting the substrate with a vaporous poly-p-xylylene precursor or a vaporous poly-p-xylylene derivative precursor admixed with a vaporous silane coupling agent to form a coating layer onto the surface of the substrate.
(9) A process for forming a coating layer comprising poly-p-xylylene or a derivative of poly-p-xylylene on a substrate, comprising the steps of:
(a) placing the substrate in a deposition chamber; and
(b) contacting the substrate with a vaporous poly-p-xylylene precursor or a vaporous poly-p-xylylene derivative precursor admixed with a vaporous silane coupling agent to form a coating layer onto the surface of the substrate, wherein at least a part of the silane coupling agent remains unvaporized in the deposition chamber during the step (b).
The invention, described in the above-mentioned item is characterized in that a parylene layer is formed on the surface of a substrate body and said parylene layer comprises a dispersed silane coupling agent. By such practice, it is possible to prepare a parylene layer which exhibits excellent adhesion to the substrate body as well as high durability, while utilizing layer performance as a parylene layer.
The invention described in the above-mentioned item is the parylene layer, described in the above-mentioned item, characterized in that said silane coupling agent is dispersed and incorporated so that some of said agent comes into contact with said substrate body. Due to that, adhesion to said substrate body, as well as durability, is enhanced. As a result, it is possible to minimize peeling of said parylene layer from said substrate body at the interface between the substrate and the parylene layer.
The invention, described in the above-mentioned item is the parylene layer described in the above-mentioned item, characterized in that the Si concentration of said coupling agent, which is incorporated into said parylene layer, within 0.1 xcexcm from the interface with said substrate body is at least 0.1 mg/cm3. By such practice, it is possible to further enhance the adhesion of said parylene layer to said substrate body.
The invention, described in the above-mentioned item, is the parylene layer, characterized in that the Si concentration of said coupling agent, which is incorporated into said parylene layer, within 0.1 xcexcm from the interface with said substrate body is 5 mg/cm3 or less. By such practice, said silane coupling agent is dispersed and incorporated into said parylene layer within 0.1 xcexcm from the interface with said substrate body, which affects the adhesion to said substrate body. As a result, said silane coupling agent exists near the interface (the interface with said substrate body) of said parylene layer in a greater amount than required, whereby it is possible to prevent a decrease in adhesion between said parylene layer and said substrate body.
The invention, described in the above-mentioned item, is the parylene layer characterized in that the Si concentration of said silane coupling agent within 0.5 xcexcm from the surface of said parylene layer is from 0 to 5 mg/cm3. By such practice, the layer performance of the surface of said parylene layer is not adversely affected by the incorporation of said silane coupling agent. As a result, said parylene layer can exhibit the desired insulating properties as well as the desired moisture resistance.
The invention, described in the above-mentioned item is the parylene layer, described in any one of the above-mentioned items, characterized in that the content ratio of the component of parylene N in said parylene layer is 50 percent or less. By such practice, it is possible to prepare a parylene layer which is more heat resistant.
The structure of parylene N is shown below.
Parylene N: Poly-para-xylylene (or Poly-p-xylylene) 
The invention, described in the above-mentioned item, is the parylene layer, described in any one of the above-mentioned items, characterized in that said parylene layer is comprised of a component of Parylene N, as well as a component of Parylene C, and when said parylene layer is divided into two layers consisting of a lower layer on the substrate body side and an upper layer on the opposite side of said substrate body, said lower layer comprises the component of said Parylene N in an amount of at least 70 percent, while said upper layer comprises the component of Parylene C in an amount of at least 70 percent. By such practice, it is possible to prepare a parylene layer which results in no pinholes, and exhibits excellent heat resistance as well as desired durability.
The structure of parylene C is shown below.
Parylene C: Poly-monochloro-para-xylylene, (or Poly-chloro-para-xylylene, or Poly-chloro-p-xylylene 
The invention, described in the above-mentioned item, is the parylene layer described in any one of the above-mentioned items, characterized in that the thickness of said parylene layer is from 1 to 10 xcexcm. By such practice, while utilizing the layer performance of said parylene layer, it is possible at low cost to quickly and easily prepare a useful protective layer, which exhibits excellent adhesion to the substrate body.
The invention, described in the above-mentioned item, is the parylene layer forming method characterized in that in a parylene layer forming method in which said parylene layer is formed on the surface of a substrate body, said parylene layer is formed under an atmosphere of a silane coupling agent, employing a gas phase synthetic method. By such practice, while utilizing layer performance as a parylene layer, it is possible to easily prepare at low cost a parylene layer which exhibits excellent adhesion to the substrate body as well as desired durability.
The silane coupling agent incorporated in the parylene layer of the present invention may react with other substance or remains unreacted.
The invention, described in the above-mentioned item, is the parylene layer forming method characterized in that in a parylene layer forming method in which said parylene layer is formed on the surface of a substrate body, said parylene layer is formed employing a gas phase synthetic method under a state in which a supplied silane coupling agent is partly vaporized. By such practice, while utilizing layer performance as a parylene layer, it is possible to easily prepare at low cost a parylene layer which exhibits excellent adhesion to the substrate body as well as desired durability.
The invention, described in the above-mentioned item, is the parylene layer forming method, described in the above-mentioned item, characterized in that during formation of said parylene layer prepared by employing said gas phase synthetic method, said silane coupling agent is completely vaporized. By such practice, while the performance of the parylene layer surface is not adversely affected by said silane coupling agent, it is possible to prepare a parylene layer which exhibits desired insulating properties as well as desired moisture resistance.
The invention, described in the above-mentioned item, is the parylene layer forming method, described in the above-mentioned item, characterized in that said silane coupling agent is completely vaporized until a parylene layer of 5 xcexcm is formed. By such practice, varying performance of the parylene layer surface is not adversely affected by said silane coupling agent. As a result, it is possible to prepare a parylene layer which exhibits desired insulating properties as well as desired moisture resistance.
The invention, described in the above-mentioned item, is the parylene layer forming method, described in any one of the above-mentioned items, characterized in that when said 0.1 xcexcm thick parylene layer is formed, a part of said silane coupling agent remains under a state of not being vaporized. By such practice, it is possible to realize a condition in which parylene and a silane coupling coexist without fail and the silane coupling agent can be incorporated in the parylene layer. It is possible to prepare a parylene layer which exhibits enhanced adhesion to the substrate body.
The invention, described in the above-mentioned item, is the parylene layer forming method, described in any one of the above-mentioned items, characterized in that said parylene layer is prepared employing said gas phase synthetic method in which Parylene N is initially supplied, and thereafter, Parylene C is supplied. Following such practice, it is possible to prepare a parylene layer which results in no pinholes and exhibit excellent heat resistance as well as desired durability.
The invention, described in the above-mentioned item, is the parylene layer forming method, described in the above-mentioned item, characterized in that during formation of a parylene layer employing said Parylene C, said silane coupling agent is completely vaporized. By so practice, it is possible to prepare a parylene layer which results in no pinholes and exhibit enhanced heat resistance as well as desired durability.
The invention, described in the above-mentioned item, is the ink-jet head characterized in that in an ink-jet head in which an electrode is provided in an ink channel, said electrode is covered with the parylene layer described in any one of the above-mentioned items, or the parylene layer which has been formed employing the parylene forming method described in any one of the above-mentioned items. Following such practice, while utilizing performance as the parylene layer, it is possible at low cost to easily prepare a useful ink-jet head which exhibits excellent adhesion to the substrate body comprising an electrode, and is provided with a highly durable parylene layer.
The invention, described in the above-mentioned item, is the ink-jet head described in the above-mentioned item, characterized in that in an ink-jet head comprising an ink channel provided with an electrode on a piezoelectric substrate, and which ejects ink from said channel by applying voltage to said electrode so that said piezoelectric substrate is deformed, said electrode is covered with the parylene layer described in any one of the above-mentioned items, or the parylene layer which has been formed employing the parylene forming method described in any one of the above-mentioned items. Following such practice, while utilizing said performance as the parylene layer, it is possible at low cost to easily prepare a useful ink-jet head which exhibits excellent adhesion to the substrate body comprising an electrode, is provided with a highly durable parylene layer, and exhibits excellent ink injecting performance.
The invention, described in the above-mentioned item, is the ink-jet head described in the above-mentioned item, characterized in that said piezoelectric substrate is a PZT substrate. Following such practice, it is possible to easily prepare an ink-jet head which is provided with a parylene layer covering the substrate body comprised of said PZT substrate in the minute ink channels and the electrode on said substrate and which exhibits excellent durability.